1、AECMA STANDARDNORMEAECMAAECMA NORMprEN 3371Edition P 1January 1994DITPAR LASSOCIATIONEUROPENNEDES CONSTRUCTEURS DEMATRIELAEROSPATIALTechnopolis - 175, rue JeanJacQues Rousseau F-92138Issy-les-Moulineaux Cedex -TI,(1) 47.36.98.76UDC:Descriptors :ENGLISH VERSIONAerospace seriesElectrical bondingTechni
2、cal specificationSMe aerospatialeMetallisationSpecification techniqueLuft- und RaumfahrtMasseverbindungTechnische LieferbedingungenThis “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA(Association Europeenne des Constructeurs de Materiel Aerospatial). It is publishe
3、d on green paperfor the needs of AECMA-Members. It has been technically approved by the experts of theconcerned Technical Committee following comment by the Member countries.Subsequent to the publication of this prestandard, the technical content shall not be changed toan extent that interchangeabil
4、ity is affected, physically or functionally, without re-identificationof the standard.After examination and signature of the AECMA Standard Checking Centre (NPS) and formalagreement of the Official SeNices of the Member countries it will be submitted as a draftEuropean Standard to CEN (European Comm
5、ittee for Standardization) for formal vote.Nota Extra copies can be supplied by B.N.A.E. - Technopolis 54 - 199. rue Jean-Jacques Rousseau - 92138 ISSY-LESMOULINEAUX CEDEXEdition approved for publication1994-01-31Comments should be sent within six monthsafter the date of publication toAECMATechnopol
6、is - 175. rue Jean-Jacques Rousseau92138 Issy-Ies-Moulineaux Cedex - FRANCEC2 ChairmanM. J. Le Cunff aecma 1994Page 3prEN 3371 : 1994o IntroductionThis document has taken into consideration Stanag 3659.1 ScopeThis standard defines the characteristics as well as the verification of bonding in on-boar
7、d aircraftelectrical systems.They refer basically to requirements relating to the effect of lightning, return currents, electromagneticinterference, as well as to the accumulation of electrostatic charges and personnel shock hazard.This standard states the maximum permissible resistance values which
8、 guarantee, according to theinstallation, good conductivity of the whole of the structure, of the whole installation and the bondingterminals; these values shall ensure correct operation of the systems.The rules of installation are defined in EN 3197.2 Normative referencesEN 3197Stanag 3659Aerospace
9、 series - Installation of aircraft electrical and optical interconnectionsystems 1)Bonding and in-flight lightning protection for aircraft 2)3 TerminologyChassis: represents the whole of the metallic parts electrically connected to each other, of a supportor piece of equipment whose potential genera
10、lly represents the reference potential (earth “0“ volt).Bonding : process of connecting together metal parts so that they make low resistance electricalcontact for direct current and low frequency alternating current.NOTE: necessary for getting a low resistant electrical current path.Grounding : the
11、 bonding of an equipment case, frame or chassis to an object or vehicle structure toensure common potential.NOTE : necessary for getting a common potential, also for keeping up a common potential at ahigh electrical fault - or lightning strike caused - current by the means of low grounding resistant
12、electrical current path which are equal to means for bonding.1 Published as AECMA Prestandard at the date of publication of this standard2 Published by : NATO, Military Agency for Standardization (MAS), B1110 BRUSSELS.Previous pageis blankPage 4prEN 3371 : 1994Earthing: the process of making a satis
13、factory electrical connection between structure, including themetal slcin of an object or vehicle at the mass of earth to ensure a common potential with the earth.NOTE: necessary for getting a common potential of the earth.Equipotential connection : an electrical connection which feeds the same pote
14、ntial to the elements ofpower production in addition to the other parts.Category I or II : the category I or II is determined by a common agreement between the aircraftmanufacturer and the Official Services.4 Primary bondingThey comprise the whole of the conducting parts of the structure, of bonding
15、 parts and conductorswhich can be traversed by considerable energy (lightning discharge currents).4.1 Main structureThe assemblies forming the structures are generally good conductors and allow the discharge of staticcharges and lightning currents.The structures are generally used as a return curren
16、t path for the sum of the currents of the on-boardelectrical installation (for example: under a current of 300 A it is usual to measure resistance from0,2 mel to 2 mel between two points about 30 m apart.4.2 Detachable partsIn principle, parts (non-articulated access doors, for example) attached by
17、a significant number ofmetallic screws shall ensure good electrical continuity and shall not require the addition of bond braids.The metallic parts attached by quarter turn screws are bonded by suitable methods (braids, contactarms, interposition of conducting materials, etc.).4.3 Articulated partsP
18、arts which are articulated and placed permanently or temporarily on the exterior of the aircraft suchas control surfaces, doors, hatches, gear legs shall be correctly bonded, taking the following twopoints into consideration:- the articulation can be, by its construction, made sufficiently conductiv
19、e even if it islubricated, provided that the contact pressure is sufficient;- the articulation is not conductive by the nature of its materials or protection used.In this instance, it is advisable to ensure bonding by a number of bond braids, ensuringredundancy and with the shortest possible length
20、arranged so as to avoid any loop or risk ofjamming during operation or by suitable means.Page 5prEN 3371 : 19944.4 Fuel tank covers and holesThe design of the tank covers shall be such that there is no danger of inflammation of vapour, shouldlightning strike these covers directly.The refuelling and
21、drainage holes, and air vents shall be carefully bonded.4.5 Engines and auxiliary starter unit 1)The main articulated attachments for the cooling system and/or ball joints shall be shunted by a braid,unless the electrical continuity between engine and structure is permanently ensured by fixedattachm
22、ent points.The fixed or moveable pipes shall also be bonded in relation to the jet engine either by construction orbraids.4.6 Non-metallic external partsThe non-metallic components, especially in areas where there is high probability of lightning (radome,wing tips and extremities of stabilizer, fin,
23、 etc.l shall be correctly protected and bonded to allowelectrostatic charges to be discharged and provide effective protection against the effects of lightning.4.7 External protruding parts4.7.1 Internal metallic parts protruding on the exterior of the aircraft (Pitot tube, drain, for example)shall
24、be bonded to the structure at a point situated as close as possible on the aircraft skin.4.7.2 Protruding parts connected to the on-board electrical circuit (sensors - Pitot tubes)Extremely good bonding is necessary to reduce possible damage to the on-board aircraft electricalsystem.4.8 Ground conne
25、ctionsTheir composition, form, section, length shall be selected in relation to the result to be obtained(minimum bonding resistance).They shall be as short as possible.The choice of attachment points shall be such that the join is as direct as possible, avoiding loops.1) The auxiliary starter unit
26、is also designated APU (Auxiliary Power Unit) in this standard.Page 6prEN 3371 : 19945 Secondary bondingThere are several groups in this category :- electrical current returns by the aircraft structure;- grounding of all metallic parts necessary for correct operation of electrical circuit protection
27、;- the discharge paths for electrostatic charges;- the grounding of electrical shielding;- the dischargers of electrostatic charges;- the earthing of the aircraft on the ground;- the grounding of equipment to avoid electromagnetic interferences.5.1 Retum of electrical currents by the structureGround
28、ing equipment or circuitsParticular care should be taken concerning the quality of electrical contact to the structure.The structural part on to which the bonding is made shall be carefully chosen.Ensure that the bonding points have adequate cross sectional area.5.2 Grounding to avoid danger of elec
29、trical shockElectrical panels or other equipment accessible to the occupants of the aircraft (circuits with voltagesof over 42 V) shall be bonded to avoid the danger of electrical shock.Articulated panels which are not detachable, attached by screws or similar metallic components, areonly provided w
30、ith braids if the contact ensured by the attachments is considered uncertain orinadequate.5.3 Discharge of electrostatic chargesThe accumulation of significant electrostatic charges on the various metallic parts or insulators of theaircarft shall be avoided by ensuring correct discharge of these cha
31、rges on the main structure of theaircraft. The electrostatic charges are discharged in flight by dischargers.The dischargers shall be fitted in sufficient number and adequately located (because of their possibleinteraction with the aerial circuits) to ensure correct discharge into the atmosphere of
32、storedelectrostatic charges.Earthing of the aircraft on the ground shall be made using earthing contacts to discharge the staticcharges, unless the tyres are conductors by design.The accessories and equipment, electrical or otherwise, shall be individually bonded.Page 7prEN 3371 : 19945.3.1 Fuel cir
33、cuitThe fuel circulation pipes shall be provided with bonding braids or be bonded by their attachment(support, clamp, etc.). the electrical continuity being ensured either by the attachment itself or bybraids arranged upstream and downstream from the attachments, or by a braid shunting theattachment
34、.The refuelling accessories shall be bonded and very carefully connected to the aircraft structure.An aircraft ground connection shall be available for the refuelling tanker in close proximity to eachrefuelling point.5.3.2 Hydraulic circuitsThe hydraulic lines shall be grounded by :their supports if
35、 bonded;their bulkhead union connections;the equipment to which they lead;additional connections if required.5.3.3 Flight controls and various mechanical controlsUnits which are operated by the occupants of the cabin (handles, pedals, control wheels, levers, seatand window controls, etc.) shall be b
36、onded.5.3.3.1 Pressurized areaThe metallic controls routed along the fuselage may be bonded solely at each of their extremities.Only the important parts included in these assemblies will be provided individually with bonding braidsor bonded by other means, thereby ensuring their grounding to the str
37、ucture.5.3.3.2 Non-pressurized areaThe parts in the non-pressurized area shall be subjected to the regulation for primary bonding.5.3.4 Air conditioning, pneumatic and airspeed circuitsThe lines shall be grounded by :- their supports if bonded;their connections, for example bulkhead union;the equipm
38、ent to which they lead;additional connections if required.5.3.5 Oxygen circuitThe bonding of the whole circuit with the fittings and corresponding equipment shall be carried outthoroughly, to avoid risks of explosion in case of a defective hose or poor bonding.Page 8prEN 3371 : 19945.3.6 External su
39、rface of the aircraftAll the non-conducting components forming the external surface of the aircraft shall be treated toavoid the accumulation of electrostatic charges and to avoid interferences with radiocommunicationand radionavigation.5.4 Equipment grounding to avoid interferencesThe values shall
40、be taken from ground reference points or from the nearest structure.5.4.1 Equipment fitted In bays or on racksThe bonding of electrical equipment fitted on racks shall be ensured by at least one of the followingmethods:bearing faces of the base plate of the equipment and the slide faces of the bay;-
41、 a pin of the equipment connector and by electrical cables of minimum section 0,60 mm2;- a bonding braid.The resistance values shall be determined in relation to the assembly mode as well as the length of thesection of conductor connected to the structure.In certain cases the grounding continuity ma
42、y also be ensured by attachments on the brackets, theguide pins and by means of a conductor shunting the shock mounts.5.4.2 Miscellaneous componentsBraids shall be provided when the attachments do not provide a good connection with the aircraftstructure.6 Measurement methods and bonding resistance l
43、imitsUse the fixed method of resistance measurement - four points - where the current-carrying circuit isindependent of the measuring circuit.6.1 Primary bonding measurementsThe primary bonding measurements in tables 1 and 2 shall be carried out on the assembled structurebefore installation of the d
44、ifferent systems.For parts defined in table 1, the current and duration of the tests shall be defined by agreement withthe Design offices.The bonding values shall be taken either between points A and B or from the ground reference pointand B.In some cases the measurements in table 1 may be replaced
45、by measurements taken between thedifferent reference points of each main section.Page 9prEN 3371 : 1994For category I, the resistance measured shall not exceed 2 mO for measurements 1 to 3 and 5 mO formeasurements 4 and 5.In other cases the resistance value shall not exceed 0,5 mO.For the use of oth
46、er materials, the value shall be determined by agreement with the Design offices.Table 1No. A Bor reference point1 Part of the main metallic structure nearest Fixed metallic part of fin nearest to the upperthe forward extremity of the aircraft extremity2 Part of the main metallic structure nearest F
47、ixed metallic structure at the extremity ofthe forward extremity of the aircraft the right wing3 Part of the main metallic structure nearest Fixed metallic structure at the extremity ofthe forward extremity of the aircraft the left wing4 Part of the main metallic structure nearest Fixed metallic str
48、ucture at the extremity ofthe forward extremity of the aircraft the right stabilizer5 Part of the main metallic structure nearest Fixed metallic structure at the extremity ofthe forward extremity of the aircraft the left stabilizerTable 2No. A B mQor reference point max.1 Reference point Part of the
49、 main metallic structure nearest 1the forward extremity of the aircraft2 Part of the main metallic structure Fuselage : fixed and removable metallic 5nearest the forward extremity of the parts (Pitot tubes, sensors, etc.)aircraft3 Part of the main metallic structure Fuselage : bonding conductors of 2nearest the forward extremity of the metallized insulating parts (radome, etc.)aircraft4 Part of the main metallic structure All metallic parts protruding on the 10nearest the forward extremity of the exterior, etc.aircraft Nose gear legs, landing gear doors5 Main aircraft structure ad
